When visiting another company i recently saw a setup where a company had 2 offices one on the 3rd floor and one on the 5th floor in the same block.

To link the 2 offices (i guess so that they where on one LAN) they had run a bunch of cat cable some in concealed risers, but some of the cable run was discreetly surface mounted.

Is this a security issue ? Would it be as simple as someone cutting the cable, putting rj45 ends on each end of the cut and placing them into a 5 port switch. Then connecting a laptop to one of the other ports on the switch to gain access to the network.

What can be done in the system / router config to prevent this ? Can the local network be encrypted on the router ?

(Other than making sure all structured cabling is properly concealed, but even then someone can cut through a 2mm thick piece of aluminium trunking.)

  • first.. is it a security issue? yes.. second.. alternatives.. Client VPN ... .. not secure per-say but something to trigger cut off.. cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/12-2/20ewa/… ... configuring port security and tying to a specific MAC. The problem.. is that someone might put a hub in there.. and listen to hear traffic ... worst case, they clone MAC directly to make it look like the device out there is still the one as its always been. access to the area, and who has that access should dictate the security polies used. – TG2 Oct 3 '16 at 10:35
  • this is what IPSEC is for, and has been around for quite some time – Neil McGuigan Oct 3 '16 at 20:41

The router can register MAC address of connected clients and reject connection by all other clients.

To make management easier, you can setup the trunk to have only two routers connected, and you will need to only explicitly allow the connection between the two routers instead of updating the MAC list every time a new device is connected.

  • Just remember to allow connections from the correct WAN/LAN side of things so you don't lock yourself out of the admin panels. – Nelson Oct 3 '16 at 10:31

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